1. Field of the Invention
The present invention relates to a plasma processing apparatus and plasma processing method for forming a silicon oxide film or silicon nitride film by processing a target object, such as a semiconductor substrate, by use of plasma.
2. Description of the Related Art
In the process of manufacturing various semiconductor devices, silicon oxide films and/or silicon nitride films are formed for use in various applications, such as gate insulating films in transistors. As a method for forming a silicon oxide film or silicon nitride film, there is a thermal oxidation process or thermal nitridation process. In addition, since it is required in recent years to decrease the temperature and thermal budget used in manufacturing semiconductor devices, there is proposed a method for performing an oxidation process or nitridation process on silicon by use of plasma to form a silicon oxide film or silicon nitride film (for example, Jpn. Pat. Appln. KOKAI Publications No. 2000-260767 and No. 2003-115587).
As a phenomenon peculiar to a plasma process for performing an oxidation process or nitridation process on silicon by use of plasma, the micro-loading effect may become prominent. Consequently, within a pattern including non-dense and dense portions and/or a pattern including different aspect ratios of trenches (the ratio of the depth of a trench relative to the width thereof) formed on a target object, a difference may be brought about in the thickness of an oxide film or nitride film between a non-dense portion or low aspect ratio portion and a dense portion or high aspect ratio portion (which will be collectively referred to as “non-dense and dense difference” hereinafter, as needed). In this case, the film thickness is smaller at a dense portion or high aspect ratio portion than at a non-dense portion or low aspect ratio portion, and the performance of semiconductor devices is thereby adversely affected, such that the leakage current increases, for example. Accordingly, it is necessary to solve this problem to prevent the reliability of semiconductor devices from being deteriorated.